Ethionic \Eth`i*on"ic\, a. [Ethyl + thionic.] (Chem.) Pertaining to, derived from, or designating, an acid so called. [1913 Webster] {Ethionic acid} (Chem.), a liquid derivative of ethylsulphuric and sulphuric (thionic) acids, obtained by the action of sulphur trioxide on absolute alcohol. Ethiop